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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Temperature-sensitive mutant | 1/3 | https://en.wikipedia.org/wiki/Temperature-sensitive_mutant | reference | science, encyclopedia | 2026-05-05T07:16:55.194576+00:00 | kb-cron |
Temperature-sensitive mutations are variants of genes that allow the organism to function normally at low temperatures but alter its function at higher temperatures. Cold-sensitive mutants are variants of genes that allow normal function of the organism at higher temperatures but altered function at low temperatures.
== Mechanism == Most temperature-sensitive mutations affect proteins, and cause loss of protein function at the non-permissive temperature. The permissive temperature is one at which the protein typically can fold properly or remain properly folded. At higher temperatures, the protein is unstable and ceases to function properly. These mutations are usually recessive in diploid organisms. Temperature -sensitive mutations arrange a reversible mechanism and can reduce particular gene products at varying stages of growth, which is easily done by changing the temperature of growth.
== Permissive temperature == The permissive temperature is the temperature at which a temperature-sensitive mutation gene product takes on a normal, functional phenotype. When a temperature-sensitive mutant is grown in a permissive condition, the mutant gene product behaves normally (meaning that the phenotype is not observed), even if there is a mutant allele present. This results in the survival of the cell or organism,as if it were a wild type strain. In contrast, the nonpermissive temperature or restrictive temperature is the temperature at which the mutant phenotype is observed. Temperature-sensitive mutations are usually missense mutations, which slightly modify the energy landscape of the protein folding. The mutant protein will function at the standard, permissive, low temperature. It will alternatively lack the function at a rather high, non-permissive temperature and display a hypomorphic (partial loss of gene function) at a middle, semi-permissive temperature.
== Developmental Effects == Temperature-sensitive mutations can significantly impact an organism's development by altering gene function at specific temperatures. These mutations affect proteins that may function normally at a lower, "permissive" temperature but become dysfunctional or degrade at a higher, "restrictive" temperature. This characteristic allows researchers to study gene function by controlling temperature conditions. One example is a mutation in the virilizer (vir) gene in Drosophila melanogaster, which prevents the proper development of female traits at elevated temperatures. This demonstrates the crucial role temperature-sensitive mutations play in regulating developmental pathways. Temperature-sensitive mutations have also been observed in human diseases. For instance, in spinal muscular atrophy (SMA), mutations affecting the Survival of Motor Neuron (SMN) protein can render it unstable at higher temperatures, leading to impaired nerve function. Researchers have developed methods to introduce temperature-sensitive mutations artificially. One approach utilizes intein-mediated protein splicing, where protein segments remove themselves under specific temperature conditions. A study by Tan et al. (2009) demonstrated how engineered inteins can regulate protein function by allowing the intein to splice at lower temperatures while remaining intact at higher temperatures, thereby disrupting protein activity. By leveraging temperature-sensitive mutations, scientists can study the functional roles of genes and proteins in both normal development and disease processes.
== Ecological Effects == At a base level, all organisms respond to their environment. Specifically, the temperature in an organism's environment can greatly impact many different aspects of its life. Understanding how temperature affects different species is difficult to study due to the fact that each one reacts differently to temperatures. Some may be more susceptible to higher temperatures due to not having the correct machinery to deal with it. Additionally, it is difficult to predict how a species would respond due to the fact that the fitness of the organism is closely intertwined with others inside of a single ecosystem [14].